As a soloist he works with major orchestras both at home in Germany, and around the world, and has given concerts with conductors including Christoph von Dohnányi, Sylvain Cambreling and Kent Nagano. Several clarinet concertos have been dedicated to and premiered by him. In 1999 he performed Musik für Klarinette und Orchester by Wolfgang Rihm as part of 'musica viva', and in 2006 Cantus by Aribert Reimann with the WDR Symphony Orchestra.
As a composer Widmann has created a trilogy for large orchestra based on the principle of transferring vocal forms to orchestral writing - Lied (premiered and recorded by Bamberg Symphony Orchestra / Jonathan Nott), Chor (premiered by the Deutsches Sinfonie Orchester Berlin / Kent Nagano) and Messe (premiered by the Munich Philharmonic Orchestra / Christian Thielemann). In 2007 Pierre Boulez and the Vienna Philharmonic premiered Widmann's new orchestral work Armonica as well as Christian Tetzlaff and the Young German Philharmonic under the direction of Manfred Honeck premiered the Violin Concerto. 2008 included the new orchestral work Antiphon with Paavo Järvi conducting the hr-Sinfonieorchester and the piano cycle Eleven Humoresques, premiered in May 2008 which has been commissioned by the Carnegie Hall New York for Yefim Bronfman. At the beginning of the 2008/09 season the Bavarian Radio Symphony Orchestra under Mariss Jansons presented his new orchestral work Con brio.
In summer 2009 he will be Artist in Residence both at the Schleswig-Hostein Musik Festival and the Lucerne Festival. Furthermore he is invited to play at the Schwetzinger Festspiele in May 2009.